The invention relates to a wrap-winding spinning machine for producing wrapped yarns, which has draw frames for attenuating slivers; in such a machine, one wrap-winding apparatus is associated with each draw frame for the purpose of wrap-winding the sliver delivered by this draw frame with at least one thin winding thread, preferably a filament, and the wrap-winding apparatus is followed by a reeling apparatus for reeling the wrapped yarn. This wrap-winding apparatus has a rotor, which is driven at very high rpm and has a yarn channel coaxial with its rotary axis; the rotor has a rotatably supported, driven hollow spindle and a bobbin interchangeably placed on the hollow spindle. The bobbin, in turn, carries the winding thread in the form of a thread winding body and is surrounded in spaced-apart fashion by a yarn-ballooning limiter having a closed circumferential wall. Finally, the yarn-ballooning limiter circumferentially surrounds the rotor head located at the top of the thread winding body located on the bobbin, forming a narrow annular gap.
The "draw frame" of the wrap-winding spinning machine is understood to be that area of one draw frame row of the machine which attenuates the sliver, the sliver serving in turn to produce a single wrapped yarn.
The slivers to be attenuated and wrapped are made up of fibers of finite length; that is, they are not endless filaments. These fibers may be, for example, cotton, wool, chemical, or cellulose fibers or any other vegetable, animal or synthetic fibers capable of being processed into wrapped yarn.
In a known wrap-winding spinning machine of this kind (disclosed in German laid-open application No. 24 28 483), the yarn-ballooning limiter is embodied as a cup closed on the bottom and fixedly disposed on the hollow spindle. The winding thread arriving from the bobbin runs from the inner wall of the yarn-ballooning limiter at a distance above the rotor head toward the yarn channel entrance of the twisting apparatus. It is unavoidable in such an arrangement that the rotating region having the winding thread, which is located between the yarn-ballooning limiter and the yarn channel, will capture fibers out of the air, fibers which may have their source in the sliver to be wrapped and also, in some cases, in the blowing-off fuzz which is inevitably present in the air in the area of the machine located in the spinning factories. The fibers caught up by the winding thread gather up into fiber tufts, specifically at that point where the winding thread leaves the yarn-ballooning limiter and in some cases also at the point where the winding thread runs over the outer edge of the end face of the bobbin, touching it. The winding thread runs through the fiber tuft and the tuft can grow larger and larger, as a result of which the thread tension of the winding thread is correspondingly greatly increased; the result can be severe fluctuations in the thread tension, which cause severe disruptions, because they cause disuniform wrap-winding of the sliver. It can also happen that the fiber tuft may be torn off after a time and carried along with the winding thread, which leads to plugging and attendant thread breaks, or an undesirable, slub-like thickening of the wrapped yarn may result.